Blending of immiscible polymers offers attractive opportunities for developing new

SynopsisThe grafting of maleic anhydride (MAn) to low density polyethylenes (PEs) dissolved in 1,2-dichlorobenzene ( DCB) has been studied. Grafting was successful a t temperatures of about 160°C both in air without initiator and under nitrogen with the radical initiator 2.5-di ( t-butylperoxy -2,5-dimethyl-3-hexyne (LPO). The presence of succinic anhydride grafts was shown by FTIR spectroscopy of the product; 'H-NMR spectroscopy indicates that the grafts consist of single succinic anhydride units. The graft content was determined by nonaqueous titration, and the extent of crosslinking inferred from the melt flow rates (MFR) of the products. The effects of concentration of initiator, MAn, and PE on the graft content were determined; the influence of PE structure, reaction time, and temperature was also studied. Melt blending of the grafted PE with polystyrene containing oxazoline functional groups (OPS) was investigated using a Rheomix mixer. The interpolymer reaction which occurs during blending was studied by means of FTIR, and the morphology of the blends by scanning electron microscopy (SEM). Information was also gained from the change in torque viscosity during the blending process.

The effects of rubber particle size and rubber/matrix adhesion on the impact properties of a brittle polymer have been separated using polystyrene (PS)/acrylonitrile‐butadiene rubber (NBR) as a model system in which interfacial chemical reaction could be controlled. It has been proven that the interfacial adhesion between the rubber phase and the PS matrix not only greatly aids in reducing the rubber particle size but also plays a further role in improving the impact properties of the matrix polymer. The impact energies of PS/NBR blends with interfacial chemical bonding are four to ten times as high as those without interfacial bonding for the same average rubber particle size. However, at temperatures below the glass transition temperature of the rubber, there is no difference in impact energies with or without interfacial chemical bonding. It has been found that the optimum rubber particle size for toughening PS is influenced by interfacial adhesion. Smaller optimum rubber particle size is observed for blends with greater amounts of interfacial chemical bonding.